This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A243089 #18 Nov 25 2019 03:30:18 %S A243089 25,325,1825,4525,4825,10225,12025,16725,20425,30025,35425,58825, %T A243089 177025,216525,265525,352225,526825,611425,675925,710425,717025, %U A243089 746425,772525,784225,834025,877825,1125825,1126225,1439425,1491025,1579225,1935025,1973425,2176525 %N A243089 Pseudoprimes to base 7 that are not squarefree. %C A243089 Any term is divisible by the square of a base 7 Wieferich prime (A123693). %C A243089 Intersection of A005938 and A013929. - _Michel Marcus_, Aug 21 2014 %H A243089 Amiram Eldar, <a href="/A243089/b243089.txt">Table of n, a(n) for n = 1..3095</a> (terms below 10^12) %o A243089 (PARI) forcomposite(n=1, 1e9, if(Mod(7, n)^(n-1)==1, if(!issquarefree(n), print1(n, ", ")))) %Y A243089 Cf. A005938, A123693, A158358, A243010, A243090, A244065. %K A243089 nonn %O A243089 1,1 %A A243089 _Felix Fröhlich_, Aug 18 2014